Gary Sharp off-loads his catch of king salmon in Quinhagak, Alaska. Nearly 95 percent of all U.S. salmon comes from Alaska, the world's largest salmon fishery. Although harvests are still healthy, they have declined due to low prices, competition from farmed salmon and warmer temperatures in the Bering Sea. (AP Photo/Tundra Drums, Danielle Wolffe)

The oceans yield nearly 100 million tons of fish annually. But global demand for seafood, combined with efficient, new fishing equipment, has driven many species nearly to extinction. Up to 75 percent of global fish stocks are overfished, according to the National Oceanic and Atmospheric Administration. The debate over saving the oceans pits conservationists, who say tighter fishing restrictions are needed to restore depleted fisheries, against commercial fishermen, who contend stocks generally are sustainably managed. The fishermen further argue that pollution, ocean shipping and coastal development are largely responsible for degrading the marine environment, rather than overfishing. Meanwhile, both sides largely agree that policies spelled out in the sweeping 1976 Magnuson-Stevens Act, now up for reauthorization, are part of the problem.